The foot-and-mouth disease virus, a member of the picornavirus family, is composed by a single stranded RNA sorrounded by a protein capsid. This capsid contains 60 copies of each of the main structural polypeptides VP.sub.1, VP.sub.1, VP.sub.3 and VP.sub.4.
During the process of inactivation to degrade the genomic RNA and inhibit the infectivity of the virus there occur alterations of the protein structure of the capsid which affect the immunogenicity of the vaccine. Since 1926, formaldehyde has been used as an inactivant for the virus (1) but it is known that formalinized vaccines contain residual infective particles (2,3). AEI (acetylethyleneimine) and BEI (binary ethyleneimine) (4,5) are better inactivants, since the infectivity of the virus is detroyed by a first order reaction. However, some strains of the virus have prooved unstable when treated with these agents, with marked deterioration of antigenicity after the inactivation (6). Also both inactivants are highly toxic.
Research carried out at the Centro de Virolog/i/ a Animal (CEVAN) led to the detection in purified foot-and-mouth disease virions of the existence of an endoribonuclease. This was the first description of the existence of an active enzyme located within a picornavirus (8, 9). This viral endoribonuclease can be activated to fragment specifically the genome, leaving fully intact capsids with immunogenic capacity, suitable for their use as vaccines.
1. VALLEE, H.; CARRE, H., AND RINJARD, J. (1926). Sur l'immunisation antiaphteuse par le virus formal/e/ . R/e/ v. G/e/ n. M/e/ d. V/e/ t. 35, 128. PA0 2. MOOSBRUGGER, G. A. (1948). Recherches exp/e/ rimentales sur la fievre aphteuse. Schweiz. Arch. Tierheilk. 90, 176. PA0 3. SCHNEIDER, B. (1955). Zur Infektiositat der Maul-und-Klausen der Absorbant Vakzine. Mn. Tierheilk. 7, 81. PA0 4. BROWN, F., HYSLOP, N. Sr. G., CRICK J. and MORROW, A. W. (1963). The use of Acetylethyleneimine in the production of inactivated Foot-and-Mouth disease vaccines. J. Hyg. Camb. 61, 337. PA0 5. BAHNEMANN, H. G. (1975). Binary ethyleneimine as an inactivant for Foot-and-Mouth disease virus and its application for vaccine production. Arch. Virol. 47, 47. PA0 6. STAPLE, R. F., MORRWO, A. W., and FLETTON, B. V. (1975). The effect of acethyleneimine upon a strain of inactivated FMDV virus stored at 4.degree.. Arch. Virol. 47, 331. PA0 7. GIRARD, H. C., BAYRAMOGLU, O., EROL, N. and BURGUT, H. (1977). Inactivation of O, FMDV virus by the binary Ethyleneimine (BEI). Bull Off. Int. Epiz. 87, 201. PA0 8. DENOYA, C. D., SCODELLER, E. A., GIMENEZ, B. H., VASQUEZ, C. and LA TORRE, J. L. (1978). Foot-and-Mouth disease virus. (I) Stability of its ribonucleic acid. Virology 84, 230. PA0 9. DENOYA, C. D., SCODELLER, E. A., VASQUEZ, C. and LA TORRE, J. L. Foot-and-mouth disease virus. (II) Endoribonuclease activity within purified virions. Virology 57, 153.